PM20618: TELNET SHUTDOWN HANGS

APAR status

• Closed as fixed if next.

Error description

• TELNET server hangs during shutdown processing.
  

Local fix

• Circumvention:  Specify NOSNAEXT in the Telnet profile.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of Communications Server for       *
  *                 z/OS Version 1 Release 10,                   *
  *                 z/OS Version 1 Release 11 and                *
  *                 z/OS Version 1 Release 12 IP Telnet          *
  *                 facilities.                                  *
  ****************************************************************
  * PROBLEM DESCRIPTION: Telnet shutdown hangs following         *
  *                      hang of connection using contention     *
  *                      resolution (SNAEXT).                    *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  The problem may be summarized as follows:
  
  1. A small number of connections were started with the
     Telnet server.  These connections negotiated contention
     resolution (SNAEXT in Telnet profile).
  
  2. A BID is sent to one of the clients during processing
     of a 3270 datastream with a corresponding SNA RH with BB.
     The client returns a positive BID response.  A Telnet
     DUCB processes the BID response and eventually issues
     an asynchronous RECEIVE RPL to VTAM:
  
     EZBTTRCV->....->EZBTVSRP->ISTAICIR->ISTAICI2->ISTAICIO
  
  3. The SRB for this thread exits but the DUCB remains, holding
     the CVB lock in shared mode.  The RECEIVE RPL is successfully
     processed by VTAM.
  
  4. Eventually the inactivity timer task suspends attempting
     to obtain the CVB lock in exclusive mode:
  
     EZBTTTMI->EZBTTCLS->EZBTTTVS->EZBITKOB->EZBITDSS
  
  4. A 'P' command is issued to terminate the Telnet server.
     This command hangs due to the these two suspended threads.
  
  5. The problem does not occur when contention resolution is
     disabled (NOSNAEXT specified in Telnet profile).
  +-------------------------------------------------------------+
  + Please check our Communications Server for OS/390 homepages +
  + for common networking tips and fixes.  The URL for these    +
  + homepages can be found in Informational APAR II11334.       +
  +-------------------------------------------------------------+
  

Problem conclusion

Temporary fix

Comments

• This APAR is being closed FIN (Fixed If Next) with concurrence
  from the submitting customer. This means that a fix to this
  APAR is expected to be delivered from IBM in a release (if any)
  to be available within the next 24 months.
  
  This problem will be tracked as Feature F151762
  by Communications Server for z/OS Development.
  
  The solution for this APAR is included in CS for z/OS Version 1
  Release 13.
  

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

Applicable component levels

• R1A0 PSN

     UP

• R1B0 PSN

     UP

• R1C0 PSN

     UP